Patent PCT/ES03/00511 describes the problems related to designing an admission gas heater for automobile thermal engines, wherein a heater of this type can be used for the following functions:                Aiding cold starts        Aiding regeneration of the particles filter        Aiding the reduction of polluting emissions        
while complying with the following requirements:                Minimal load losses        Short response times        High power dissipation capability.        
This document explains how these design requirements make it necessary to design heaters with dissipation resistors that must work at very high temperatures, so that in order to operate such a heater without overheating risks it is necessary to incorporate sensors for measuring the temperature of its support, which may be in contact with plastic materials that must not exceed a certain temperature, which for the plastics commonly used in the industry is on the order of 150° C. This heater module with an incorporated electronic temperature control allows managing the dissipated power efficiently according to said measurement and eliminates the risk of deformation or fire in the plastic parts in contact with the heater.
However, an analysis of the failure modes of this heater module reveals the following risks:                1. In case of short-circuit of the power switch in the control circuit, the resistor will be constantly connected to the battery; if the heater module is mounted on a plastic collector nothing will prevent the temperature from rising continuously, deforming said collector due to overheating or setting fire to it, in turn resulting in an engine fire.        2. The control embodied as described in the cited patent PCT/ES03/00511, is effective because it is based on the measurement of the support temperature and limits the power dissipated by the heating resistors in order to keep said temperature under a given safety value; however, this control has the added risk of the support being heated due to power dissipation in the power switches, so that the management of the power supplied to the air flow will be erroneous.        
As regards the measurement of the resistor temperature, invention patent PCT/ES02/00369 describes a “system for controlling the temperature of the admission air in Diesel internal combustion engines” which claims a heater with resistors made by soldering to strips of different metal alloys such that they will dissipate power while, as they are made from the union of two different metals, their thermocouple function will allow knowing the resistor temperature. However, a heater manufactured with resistors of this type does not reduce the aforementioned risk of a poor operation of the control circuit and overheating, with the resulting risk of fire.